The present invention relates to aircraft comprising foldable wings, and to rotational joints for use on such aircraft.
There is a trend towards increasingly large passenger aircraft with higher performance efficiency (for example fuel burn reduction), for which it is desirable to have correspondingly large wing spans. However, the maximum aircraft span is effectively limited by airport operating rules which govern various clearances required when maneuvering around the airport (such as the span and/or ground clearance required for gate entry and safe taxiway usage).
In some suggested designs, aircraft are provided with wings which may be rotated such that part of the wing is folded to reduce the span of the aircraft on the ground (compared to when the aircraft is configured for flight).
However, a disadvantage with such arrangements is that the wing tends to have limited volume in the vicinity of the rotational joint between the fixed and folded parts of the wing. In order to accommodate essential internal structure (e.g. ribs, spars or other support structure), and/or aircraft systems (e.g. actuators) within the wing, it may be necessary to redesign the internal layout of the wing, locally increase the wing volume in the vicinity of the rotational joint, and/or significantly constrain the possible location of the rotational joint. This can negatively impact the design of the aircraft.
The present invention seeks to address or mitigate at least some of the above mentioned problems. Alternatively, or additionally, the present invention seeks to provide an improved aircraft with a wing tip device that is rotatable relative to the fixed wing. Alternatively, or additionally, the present invention seeks to provide an improved rotational joint for a rotatable wing tip device.